1. Field of the Invention
The present invention relates to a resist composition and a method for manufacturing a semiconductor device using the resist composition. In particular, the present invention relates to a resist composition suitable for fine processing of a semiconductor device using ArF excimer laser as a light source.
2. Description of the Background Art
A semiconductor integrated circuit has been highly integrated and a minimum pattern width in the integrated circuit has become to a level of sub-half microns. Further, such device has been being finer. A lithography technique on which such finer processing is based generally comprises the steps of: applying a resist on the surface of a substrate to be processed to form a photosensitive film; irradiating the resist with a light to delineate a given pattern; heating, if necessary, the resist; developing the resist to form a desired fine pattern; and processing the substrate to be processed by, e.g., etching using the fine pattern as a protection film.
A lithography technique by which a fine pattern of 0.18 xcexcm or less is formed has been recently required. As an approach for the finer pattern, a reduction in a wavelength of exposure light used during patterning of a resist has been investigated.
Conventionally, the i-line in a high-pressure mercury-vapor lamp (wavelength: 365 nm) has been used as a light source for manufacturing a DRAM with an integration degree up to 64 M bits.
KrF excimer laser (wavelength: 248 nm) has been practically used as an exposure light source in place of the i-line for mass production of a 256 M bit DRAM.
Now, a further shorter light source has been investigated, aiming at manufacturing a DRAM with an integration degree of 1 G bit or more, and the use of ArF excimer laser (wavelength: 193 nm), F2 excimer laser (wavelength: 157 nm), X-ray and electron beam is believed to be effective. Among these light sources, ArF excimer laser lithography with a higher resolution may be promising.
In conventional lithography using the i-line, an alkali-soluble phenol resin such as a novolac resin has been used as a base resin for a resist composition in order to provide higher dry etching resistance.
The alkali-soluble phenol resin shows good transmittance for the i-line while exhibiting poor transmittance for far ultraviolet or vacuum ultraviolet ray with a shorter wavelength. In particular, for an exposure light from ArF excimer laser as a light source, transmittance is extremely reduced due to optical absorption by an aromatic ring in the resin.
Thus, an exposure light with a shorter wavelength cannot adequately sensitize a resist film to the bottom and therefore, does not form a resist pattern with a good cross section. In other words, it does not provide an adequate resolution.
So, a methacrylate copolymer resin without an aromatic ring has been investigated as a resin exhibiting good transmittance to an exposure light with a shorter wavelength.
However, dry etching resistance may be significantly reduced without an aromatic ring in a resin. To solve the problem, there has been disclosed a polymer having an alicyclic hydrocarbon group such as adamantyl and norbornyl group in an ester moiety.
It is, however, difficult to form an even applied film with good reproductivity because a homopolymer of the monomer with the alicyclic hydrocarbon group is highly hydrophobic and exhibits poor adhesiveness to a substrate to be processed (for example, a silicon substrate). It may, therefore, lead to poor development properties or lower resolution.
Thus, a copolymer comprising a copolymer component improving development properties or a copolymer component improving adhesiveness has been added to the resin to be used as a base resin of a resist component.
However, since the content of the copolymer must be about 50 mol % or more, it may significantly deteriorate dry etching resistance, leading to poor practicability.
As described above, an adequate alicyclic hydrocarbon group has not been contained in components in a conventional resist composition using an alicyclic methacrylate exhibiting good transmittance to a short-wavelength light such as ArF excimer laser as a base resin.
Thus, it may lead to lower resistance to dry etching conducted after forming a resist pattern, to reduction in a film thickness of a resist pattern and to poor mask linearity.
There has been, therefore, a defect in a conventional resist composition that a resist pattern fails to be correctly transferred to a substrate to be processed.
The present invention has been conceived to solve the previously-mentioned problems and a general object of the present invention is to provide a resist composition exhibiting good resolution to a far ultraviolet ray with a wavelength of 250 nm or less, in particular ArF excimer laser beam, and is to provide a resist composition exhibiting good dry etching resistance.
The above object of the present invention is attained by a following resist component and a following method for manufacturing a semiconductor device.
According to one aspect of the present invention, the resist composition comprises: at least one type of a first compound having two or more intramolecular adamantyl structures; a base resin; and a second compound which generates an acid by active beam irradiation.
In one aspect of the present invention, the resist composition further comprises preferably a nonion surfactant.
In one aspect of the present invention, the resist composition further comprises preferably an amine.
According to another aspect of the present invention, the method for manufacturing a semiconductor device comprises: an application step of forming a resist film by means of applying the resist composition according to the one aspect of the present invention onto a substrate; a pre-exposure heating step of heating the resist film formed in the application step; an exposure step of exposing the resist film by means of irradiating the resist film with an active beam via a given mask after the pre-exposure heating step, the active beam having a wavelength of 150 to 250 nm; a post-exposure heating step of heating the resist film after the exposure step; a development step of forming a resist pattern by means of developing the resist; and an etching step of conducting dry etching with the resist pattern as a mask.